42 Week Old Baby Development

Learn everything you need to know about your 42 week old baby. Track important developments and milestones such as talking, walking, growth, memory & more.

Baby boy lying on bed
Photo: Getty Images/ Jessica Peterson

Your Growing Baby

Brain Booster

Your baby's getting smarter every day! At 10 months, he's starting to grasp concepts such as time, distance, depth, and cause and effect, and he'll incorporate them into his play. For example, he might stack different-size rings on a plastic cone, knock them down, then stack them up in a new order to see how they look this time. He'll roll a ball to you, expecting that you'll send it back his way. He might separate Cheerios from the diced peaches on his breakfast plate, a sign he's learning to identify and sort different shapes, colors, and textures. Your baby continues to learn about the properties of objects by crumpling, ripping, tasting, and throwing anything he can get his increasingly dexterous hands on.

And what a personality he's getting! Kids this age begin to show a huge range of emotions—from fear and sadness to twinkle-eye glee—and everything in between. Baby might look sheepish when you catch him doing something forbidden; expectant when you put him in his high chair; and excited when he sees someone he loves. Some babies start showing surprisingly grown-up traits these days. They might smack their lips and murmur, "Mmm!" when they taste something yummy, stamp their feet in time to music, or even daydream, staring off into space as though they have a lot on their minds. Encourage your baby to express himself—and help him learn the actual words to describe how he's feeling—by saying things like "You look so excited, honey!" or "Isn't that delicious?"

Health and Safety Info

Moving to a Sippy Cup

Pediatricians generally recommend that babies switch from bottles to sippy cups by their first birthday, since sucking on a bottle after that can lead to cavities and other dental issues. For some kids, the switch is no big deal, but for others, particularly those who have been drinking from a bottle since birth and now view it as an object of attachment, it takes a lot of getting used to. Your child might flat-out refuse the sippy, cry, or struggle even figuring out how to get the sippy cup into his mouth.

To make the transition easier for both of you, start introducing a sippy cup now, if you haven't already. Buy a small cup with easy-to-grasp handles on both sides and fill it halfway with breast milk, formula, or diluted juice. Then show Baby how pick it up, bring it to his mouth, and tip it to drink. He might just play with it at first, which is why it's best to buy the no-spill kind, but eventually he'll get the idea. You can offer him sippy cups in addition to his usual bottles for a few weeks, then slowly phase out the bottles. If he still wails for one, try filling it with water and using the cup to offer formula or juice, which he probably likes better. Eventually he should lose interest in the bottle. But don't worry if he's still hooked at the 12-month mark. Eventually he'll make the change.


Mommy Workouts

Confession time: When was the last time you exercised? If you're like a lot of moms, it's probably been weeks, maybe even months. And who can blame you! Between your baby, work, chores, and your hubby, it's hard to find two minutes to breathe, let alone work out. But it's worth carving out some sweat time. Exercise is one of the best anxiety- and stress-busters out there, and surprisingly, regular workouts will leave you with more energy to chase your little one. Plus, by squeezing in 30-40 minutes of cardiovascular exercise each day, you'll be adding years to your life—extra time that lets you see what your child is up to in middle age.

Of course, knowing the benefits of exercise doesn't give you more time to do it. That's why many fitness experts suggest breaking up your workouts into three or four manageable 10- or 15-minute mini sessions, which do your body just as much good as one long workout done for the same total amount of time. So hop on the exercise bike while your baby dawdles over breakfast. Squeeze a brisk walk into your lunch hour. Or do some strength exercises while you watch "Law and Order" at night. Adding a bit of extra activity to your day—by, say, parking in the last space when you're headed to Target—can lead to a happier, healthier lifestyle.

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